Check for system-wide installed package update

[Reza Alizadeh Majd]

Hi Guix, 

adding the package names to package list in system configuration file, 
we could install these packages system wide and they will be available 
for all users. 

for packages that are located in user profile, we could check for available
updates using `guix pull`. 

but I didn't find any similar concept for system wide installed packages. 

is it possible to check for system wide installed packages without 
reconfiguring the system? 



PS: I need to apologies about my previous message in mailing list that
was totally a mess, and  my recently using mail client broke the message
format. 

--
Regards
Reza Alizadeh Majd
PantherX Team